This invention relates in general to extruding devices and in particular to a new and useful device for producing a helically wound tube.
This invention relates to a device for the production of a tube, container, or like cylindrical object (hereafter referred to simply as a tube) by the helical winding of a thermoplastics profile section molded in an extruder having an extrusion head onto a mandrel, in which a profiled pressure member of a width at least corresponding to the width of the plastics profile section and which welds together the abutting and/or overlapping edge regions of the wound plastics profile section, is displaceable along with the extruder in the axial direction relative to a power-driven rotating mandrel.
In one known device of this type (DAS 14 50 348), the extrusion head is disposed with its longitudinal axis normal to the axial direction of the mandrel and coincident with a secant of the mandrel and is adapted to extrude the plastics profile section as a hollow section having internal reinforcements, while the pressure member consists of a profiled roller freely rotatable about an axis parallel to the mandrel axis, on which the plastics profile section is bent against the curvature of the mandrel surface and simultaneously squeezed down. The major disadvantage of this device is to be seen in that the forming of the extruded plastics profile section by means of the profiled roller is very difficult to control and is subject to such large variations that the physical and technical properties of the resulting tubes, for example their load-carrying capacity, cannot be accurately predicted and substantial safety margins must therefore be allowed.